The present invention relates to fluid-flow control devices, and to fluid distribution systems including a plurality of such devices. The invention is particularly useful with respect to water irrigation systems, and is therefore described below with respect to that application.
In water irrigation systems supplying water to a plurality of sprinklers, there is a continuous drop in the water pressure from the upstream end of the supply line to the downstream end, so that, unless this is corrected, the downstream sprinklers will distribute less water than the upstream sprinklers. This variation in the water pressure along the line may also be caused by the sprinklers being at different elevations. For these reasons, pressure regulators are commonly included within the branch lines, or within the sprinklers themselves, to maintain a substantially constant outlet pressure. Pressure-regulators, however, are expensive to produce to install, and to maintain. Moreover, where the sprinklers include small-orifice nozzles, for example in under-tree sprinkling at a rate of about 100 liters per hour, the pressure regulators commonly include small passageways which are easily cloggable and which therefore require frequent cleaning.